1. Field of the Invention
The present invention relates to a bonded membrane-electrode assembly having water-electrolyzing and power-generating functions, and particularly, to a bonded membrane-electrode assembly including a solid polymer electrolyte membrane, and an oxygen electrode and a hydrogen electrode which are bonded to opposite sides of the membrane, and to a fuel cell system provided with a water electrolyzer, which can be used as a fuel cell including a hydrogen-generating device utilizing the bonded membrane-electrode assembly.
2. Description of the Related Art
At present, a fuel cell attracts a great deal of attention as a generator tender to an environment and having a high efficiency, and has been developed so that it can be put to practical use. In the fuel cell, hydrogen, LPG (liquefied natural gas), alcohol or the like is used as a fuel, but particularly, if an environment is taken into consideration, hydrogen is most preferable, and hydrogen supplied from a bomb containing hydrogen sealedly incorporated therein or a bomb containing a hydrogen-absorption alloy incorporated therein is utilized.
To obtain hydrogen for this purpose, the electrolysis of water is carried out, and an apparatus for generating hydrogen by the electrolysis of water includes, particularly, a hydrogen-generating apparatus using an ion exchange membrane with brine such as sea water used as a supply water (for example, see JP-A-2000-64080).
An insoluble electrode used for the electrolysis of brine includes an electrode whose base material can be inhibited from being damaged under a high current density condition and under a high voltage condition, but also includes a platinum-iridium based electrode which has a high hydrogen-generating efficiency and whose long life can be achieved (for example, see JP-A-11-269688).
In such a water electrolyzer for carrying out a process for producing hydrogen, in general, hydrogen is generated by supplying an electric current in a state in which water is acidic or alkaline. In this case, an acid or base used is strongly acidic or strongly alkaline, resulting in a problem in safety.